Shopping cart

ABSTRACT

The present invention teaches and discloses method and apparatus for alerting a grocery store check out cashier of merchandise placed on the bottom tray of a typical grocery shopping cart. A passive RFID transponder is incorporated into the structure of the cart which when interrogated by an associated reader, located at the cashier&#39;s check out station, responds with a signal verifying the presence, or absence, of an unseen item upon the cart&#39;s bottom tray.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 11/209,501 filed on Aug. 23, 2005, now U.S. Pat. No. 7,242,300, which claims the benefit of Provisional Patent Application Ser. No. 60/604,808, filed on Aug. 27, 2004, and of Provisional Patent Application Ser. No. 60/642,556 filed on Jan. 11, 2005, each of which is hereby incorporated reference herein.

FIELD OF THE INVENTION

The field of the present invention generally relates to Radio Frequency Identification (RFID) technology. More specifically the present invention relates to using RFID technology to detect the presence of merchandise placed upon the bottom try or rack of a typical grocery shopping cart by a consumer.

BACKGROUND

A typical grocery shopping cart as used in grocery stores comprises a base frame, supporting wheels and a bottom rack or tray for carrying large bulky purchases such as bags of dog food and the like, an upper basket extending over top of the bottom tray, and a handle bar for pushing the cart about the store.

When the top basket is relatively full, items placed upon the bottom tray are, many times, hidden from view and may go unnoticed by the check out cashier.

Thus an effective means is needed to detect items, placed on the bottom tray of a grocery shopping cart, that may be hidden from view of the check out cashier.

SUMMARY

The present invention teaches an improved method and apparatus for the detection of articles of purchase placed upon the lower shelf or tray of a typical grocery shopping cart at the check-out cashier's station that otherwise may go unnoticed.

Our invention comprises a weight sensing grocery cart, bottom tray, employing a passive RFID transponder module that will respond to an interrogating RFID signal, as the grocery cart is passed through a grocery cart check out station, when a product is present upon the grocery cart bottom tray.

Products placed upon the grocery cart's bottom tray are detected by a logic sensing radio frequency microchip and antenna incorporated into the bottom tray. A radio frequency identification transmitter/receiver with an antenna is located in the check out station area and coupled to an alert warning device located in proximity of the check out cashier, or coupled to an otherwise automated system that alerts the check out cashier to the presence of an unnoticed product on the bottom tray of the grocery cart.

When an item is placed on the grocery cart's bottom tray, the item activates a weight sensing switch mechanism incorporated within the bottom tray. As the tray is passed through the check out station detection area, the radio frequency transmitter/receiver, in the detection area, activates a microchip incorporated into the cart's bottom tray. The microchip then senses the state of the weight sensing switch mechanism within the tray and transmits this information back to the check out station transmitter/receiver. A signal is then sent to an alert device whereby the “operator” is notified of the presence of an item on the bottom tray. The “operator” may be a person, namely a check out cashier, or may be hardware such as a computer or programmable logic controller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a side elevation view of a typical grocery shopping cart according to a preferred embodiment.

FIG. 2 presents a rear elevational view of the grocery shopping cart in FIG. 1 shown passing through a typical grocery store cashier's check out station.

FIG. 3 presents a top view of the lower shelf of the grocery cart shown in FIG. 1 and taken along lines 3-3 in FIG. 1.

FIG. 4 is a bottom view of the lower shelf of the grocery cart shown in FIG. 1 and taken along lines 4-4 in FIG. 2.

FIG. 4A is a crossectional view taken along line 4A-4A in FIG. 4.

FIG. 4B is a crossectional view taken along line 4B-4B in FIG. 4.

FIG. 4C is a crossectional view taken along line 4C-4C in FIG. 4.

FIG. 4D is a crossectional view taken along line 4D-4D in FIG. 4.

FIG. 5A is a crossectional view taken along line 5A-5A in FIG. 3.

FIG. 5B is a crossectional taken along line 5B-5B in FIG. 3.

FIG. 6A is a crossectional view taken along line 6A-6A in FIG. 4.

FIG. 6B is a crossectional view taken along line 6B-6B in FIG. 4.

FIG. 7A is a crossectional view taken along line 7A-7A in FIG. 4.

FIG. 7B is a crossectional view taken along line 7B-7B in FIG. 4.

FIG. 8 presents a schematic of the passive transponder circuit on the shopping cart shown in FIG. 1.

FIG. 9 presents a schematical illustration of a reader system that may be installed at a typical cashier's check out station.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a typical grocery store shopping cart 10 commonly used in modern day supermarkets. Shopping cart 10 generally comprises a basket 12 for receiving the shoppers selected purchases, an undercarriage structure assembly 14 for supporting basket 12, and providing a handle 16 for pushing the cart and supporting wheels 18.

As illustrated in FIGS. 1 through 3, a bottom tray assembly 20, supported by undercarriage 14, is typically provided for the placement of large and/or bulky items selected for purchase. In the present embodiment of the invention tray assembly 20 is hingedly supported at the front end of cart 10 by hinged support assembly 25 and at the rear by a laterally extending support bar 22. Hinge support assembly 25 attaches bottom tray 20 to the front end of undercarriage assembly 14 and permits the rear portion of bottom tray 20 to be raised and lowered, thereby permitting the telescopingly storage of carts 10 when not in use. Hinge support assembly 25 also permits bottom tray 20 to “float” vertically as described in further detail below.

Turning now to FIGS. 4 through 4D, bottom tray assembly 20 primarily comprises a planar grid structure having a multiplicity of longitudinal longerons 30 and laterally intersecting orthogonal members 32 within a surrounding frame 34. Included within the planer grid structure of bottom tray assembly 20 is a planer rectangular structure 35 comprised of enlarged portions of intersecting longerons 38 and 39 and orthogonal members 40 and 41. Extending longitudinally outward from opposite sides of rectangular structure 35 are similarly enlarged longerons 42 and 44 extending forward toward the front end of tray 20 and toward the rear of tray 20 respectively.

Referring now to FIGS. 3, through 5B, the forward portion of surrounding frame 34 includes a “floating” hinge assembly 50 comprising an inverted “U” shaped channel member 52 that engages front end support rod 45. Support rod 45 comprises a single rod extending through the lateral length of hinge assembly 50 and is affixed to cart undercarriage assembly 14 as best illustrated in FIG. 3.

At opposite lateral ends of channel member 52 are vertically aligned compression springs 62A and 62B positioned between support rod 45 and the top of channel member 52 whereby tray assembly 20 floats a predetermined distance above support rod 45 and is also free to rotate about support rod 45 thereby permitting carts to be telescopingly stored when not in use.

Referring now to FIGS. 3, 4, 6A and 6B. The rear portion of tray 20 includes rear channel support member 61 having rear support bar 22 passing therethrough as best illustrated in FIGS. 6A and 6B. Similar to the forward portion of tray 20, a pair of oppositely positioned, vertically aligned, compression springs 65A and 65B are positioned between rear support bar 22 and the top of rear channel support member 61 as best illustrated in FIGS. 6A and 6B. Compression springs 65A and 65B cause the rear portion of tray 22 to float at a predetermined distance above rear support bar 22.

By the action of compression springs 62A, 62B, 65A and 65B tray 20 floats above forward support rod 45 and rear support bar 22.

Referring now to FIGS. 4, 7A and 7B. An electrical “on-off” switch assembly 76 and 78 is positioned within rear channel 61 and front channel 52. Switch 76 is positioned above rear support bar 22 and switch 78 is positioned above front support rod 25 as illustrated in FIGS. 7A and 7B. Switches 76 and 78 are simple on/off, single pole/single throw, switches having a suitable plunger type operator 77 and 79 respectively. Although only two on/off switches are illustrated, any number of on/off switches may be used as desired.

In operation, tray 20 is floatingly suspended above front support rod 22 and rear support bar 25 by action of compression springs 62A, 62B, 65A, and 65B such that switches 76 and 78 are in the non-activated (open) configuration. When an object is placed upon tray 20, the appropriate compression spring, or springs 62A, 62B, 65A and/or 65B are compressed whereby at least one of the switches, 76 or 78, is activated (closed) by switch plunger 79 and/or 78 coming into contact with front support rod 45 and/or rear support bar 22.

Turning now to FIGS. 4 and 8, a passive transponder device is attached to, or otherwise integrated into, enlarged orthogonal members 40, 41, and longerons 38 and 39. Attached to or otherwise integrated therewith, is an onboard transponder microprocessor module 46 having therein microprocessor 70 and associated elements as illustrated in FIG. 8.

The passive transponder circuit comprises antenna 82, capacitor 72, for tuning antenna 82, and one or more weight sensing switches 76 and 78 wired in series with resistor 74 by way of hard wiring 84 and 86 extending through enlarged longerons 42 and 44 as best illustrated in FIGS. 4C and 4A respectively. A suitable microprocessor chip 70 is Microprocessor Model MCRF-202 manufactured by Microchip, Inc., of Chandler, Ariz. Antenna 82 comprises multiple loops of cooper wire embedded within, or otherwise attached to orthogonal members 40 and 41 and longerons 38 and 39 of tray 20 thereby forming a loop antenna. See FIGS. 4B and 4D. Capacitor 72 is arranged in parallel with antenna 82 thereby tuning the natural frequency of the circuit to maximize response at the desired operating frequency within the range of 100 to 400 kHz. Other frequencies may be used, however, the range of 100 to 400 kHz has been found to provide the preferred read range and antenna size.

FIG. 2 illustrates a typical grocery store cashier's check out station 26 embodying the present invention. Contained within check out station 26 is an RFID Inc. Model 5000-1E-RW transponder reader 92 with an associated RFID Inc. Model 5160 Reader Head antenna 94 (manufactured by RFID Inc., of Aurora, Colo.) embedded within floor 100.

Tray 20 contains no active power source. Power for the passive transponder circuit is generated by the reader antenna 94 exciting an oscillating electromagnetic field at a frequency corresponding with the natural frequency of the tuned transponder antenna 82. The oscillating electromagnetic field from reader antenna 94 causes electrical currents to oscillate in antenna 82 of the on board transponder. Microprocessor chip 70 rectifies this current and converts the energy into a DC voltage current source sufficient to operate microprocessor 70,

Upon powering of microprocessor 70, a voltage is applied across parallel switches 76 and 78, in series with resister 74, and a voltage is sensed by the microprocessor sensor pin between resister 74 and switches 76 and 78. In the event switches 76 and 78 are in the open state, thereby indicating that no items are present on tray 20, the voltage sensed is in a high state because no voltage drop across resister 74 has been detected.

However, if at least one switch, 76 or 78, is closed, thereby indicating the presence of an item upon tray 20, the voltage sensed is in a low state because a voltage drop across resister 74 has been detected.

Upon sensing the state of voltage in hard wiring 84, microprocessor 70 will transmit a pre-programmed bit pattern by momentarily grounding, or otherwise disturbing transponder antenna 82 in a predetermined manner thereby modulating the amplitude of the transponder antenna 82 voltage and resulting emitted radio frequency signal amplitude. The bit pattern must be transmitted with a predetermined protocol, such as Manchester, Frequency Shift Keying (FSK), or any other serial data transmission protocol, to allow the reader 92 to properly interpret the data being received from transponder module 46.

The transponder antenna disturbance and resulting radio frequency signal is sensed by reader antenna 94 and transmitted to reader module 92 through hard wiring 93 and therein converted, by reader module 92, back into the original digital bit pattern. This bit pattern may be further processed by reader module 92 and transmitted through hard wiring 95 to any external system, such as a visual monitor 96, store database 94 or any other suitable alert devise 98.

The preferred location of reader antenna 94, in a retail store application, is embedded in the floor 100 adjacent the cashier's check out stand 26 where customers typically unload the cart as illustrated in FIG. 2. It may be desirable to place a second reader antenna down stream of the first reader antenna 94 to check that an object detected by the first reader antenna had, in fact, been removed. Thus the cashier may be assured that all items have been accounted for before the transaction can be finalized.

The transponder microprocessor 70 is configured to transmit a string of bits to reader 92 when interrogated. The bit pattern transmitted may be configured and stored in the read only memory of microprocessor 70 in any number of ways to allow for identification of the particular grocery cart by a unique serial number, cart manufacturer, state of the weight sensing switches 77 and 79, an/or any other information that may be encoded in a bit stream.

Microprocessor 70 may transmit a pre-programmed bit pattern normally or inverted, depending on the state of weight sensing switches 77 and 79, thus if all switches are in the open condition, indicating that tray 20 is empty, the bit pattern will be transmitted normally. However, if one of the switches 77 or 79 is closed an inverted bit pattern would be transmitted. This feature may provide for self-diagnostics of tray 20. Thus if the cart passes through the detection area and no bit stream is transmitted, the cashier may be alerted to a defective transponder on that particular grocery cart.

It is evident that many alternatives, modifications, and variations of the present invention will be apparent to those skilled in the art in light of the foregoing teachings. Accordingly, the invention is intended to embrace all such alternatives, modifications, and variations as may fall within the spirit and scope of the appended claims. 

1. A weight sensing system for use with a cart and an interrogating system, the system comprising: a tray assembly configured to attach to the cart; a weight sensing system configured to detect one or more items on the tray assembly based at least in part on the weight of the one or more items; and a passive radio frequency transponder system on the cart, wherein the transponder system is connected to the weight sensing system; wherein the transponder system is configured to transmit a signal when interrogated by the interrogating system, said signal for indicating the presence of the one or more items detected by the weight sensing system.
 2. The weight sensing system of claim 1, wherein the transponder system is further configured to transmit a second signal for indicating the absence of one or more items on the tray assembly.
 3. The weight sensing system of claim 1, wherein the cart is a shopping cart.
 4. The weight sensing system of claim 3, wherein the shopping cart comprises an undercarriage structure assembly to which the tray assembly is configured to attach.
 5. The weight sensing system of claim 4, wherein the tray assembly is hingedly supported at a front end of the undercarriage structure assembly, whereby the shopping cart may be telescopingly stored with other carts when not in use.
 6. The weight sensing system of claim 1, wherein the transponder is integrated in the tray assembly.
 7. The weight sensing system of claim 6, wherein transponder comprises a loop antenna tuned to between 100 kilohertz and 400 kilohertz.
 8. The weight sensing system of claim 1, wherein the tray assembly comprises one or more weight sensors.
 9. The weight sensing system of claim 8, wherein at least one of the one or more weight sensors comprises a switch and a biasing mechanism.
 10. The weight sensing system of claim 9, wherein said switch is a single pole, single throw switch, and said biasing mechanism is a spring.
 11. The weight sensing system of claim 1, wherein the interrogating system comprises a transponder reader.
 12. The weight sensing system of claim 11, wherein the transponder reader comprises a radio frequency transponder.
 13. The weight sensing system of claim 12, wherein the radio frequency transponder comprises a Radio Frequency Identification (RFID) transponder.
 14. The weight sensing system of claim 1, further comprising a processor configured to detect an output from the weight sensing system.
 15. The weight sensing system of claim 14, wherein the processor is configured to generate a predetermined bit pattern with information comprising a weight sensor state.
 16. The weight sensing system of claim 14, wherein the processor has no active power source and receives power from the interrogating system.
 17. The weight sensing system of claim 16, wherein the power received from the interrogating system is received via the transponder system.
 18. The weight sensing system of claim 17, wherein the transponder system is configured to rectify a voltage from an antenna excited by the interrogating system.
 19. The weight sensing system of claim 1, further comprising a warning device configured to generate an alert based on the sensed weight.
 20. A weight sensing system for use with a cart and an interrogating system, the system comprising: a tray assembly configured to attach to a shopping cart; a weight sensing system configured to detect one or more items on the tray based on their weight; and a passive Radio Frequency Identification (RFID) transponder on the shopping cart; wherein the transponder is configured to transmit a signal when interrogated by the interrogating system, said signal indicating: a) the presence of the one or more items detected by the weight sensing system; or b) the absence of one or more items on the tray assembly.
 21. A weight sensing system comprising: an RFID interrogating system; a shopping cart comprising: a) a tray assembly; b) a weight sensing system configured to sense a weight of one or more items on the tray; and a passive Radio Frequency Identification (RFID) transponder comprising an antenna, wherein the transponder is configured to acquire power from the RFID interrogating system with the antenna, and to transmit a signal when interrogated by the interrogating system, said signal indicating: the presence of the one or more items detected by the weight sensing system, and the absence of one or more items on the tray assembly; and a warning device configured to generate an alert based on the sensed weight.
 22. A weight sensing system for use with a cart and an interrogating system, the system comprising: a tray assembly configured to attach to the cart; a weight sensing system configured to detect one or more items on the tray assembly based at least in part on a weight of the one or more items; and a passive radio frequency transponder system on the cart, wherein the transponder system is connected to the weight sensing system; wherein the transponder system is configured to transmit a signal when interrogated by the interrogating system, said signal for indicating the weight detected by the weight sensing system. 